Pulpectomy has widely been performed for treatment of pulpitis, which includes removal of the dental pulp, enlargement and cleaning of the root canal. Various devices have been proposed for performing such a treatment, including hand reamers, engine reamers, and engine files.
An example of an endodontic handpiece for electrically driving a cutting tool, such as a reamer or a file, used for root canal therapy is schematically shown in FIG. 4. The endodontic handpiece includes handpiece body 1A generally in an elongated cylindrical form, and head unit 1B detachably threaded onto the handpiece body 1A. The handpiece body 1A accommodates therein a motor driven by, for example, an external power supply or a rechargeable battery. This motor is operated by pressing power switch 4 provided projecting on the handpiece body 1A in its distal portion. The head unit 1B includes neck section 2 and head section 3 integrally connected to the distal end of the neck section 2. Cutting tool 5 is detachably mounted on the head section 3 and driven by the motor for endodonic treatment.
During treatment with such an electrically driven handpiece, it is demanded that the same handpiece is also capable of precisely measuring the length of the root canal. For this purpose, there have been proposed handpieces that employ the cutting tool as a probe to enable measurement of the length of the root canal during the root canal therapy.
For example, JP-9-224961-A discloses a handpiece having a root canal length measurement function, which enables measurement of the root canal length while giving the root canal therapy. This handpiece has incorporated inside a signal circuit for sending measurement signals from a root canal length measurement circuit to a measurement probe mounted on a head provided at the tip of the handpiece, and the signal circuit is electrically connected to the measurement probe via a contact piece. The contact piece is provided on the lower surface of the head and supported so as to be rotatable vertically in the axial direction of the measurement probe. The contact piece holds the measurement probe between the tip portions thereof when rotated in the upward direction that makes contact with the measurement probe.
In this handpiece, the contact piece is made vertically rotatable on the lower surface of the head by pivotally connecting the contact piece to a separately provided contact plate, which requires bothersome production and assembly of these parts. Further, possibility of improper contact between the contact piece and the contact plate in the pivoting region cannot be eliminated.